Manufacture of lithopone



- UNITED STATES PATENT OFFICE.

, JOHN L. MITCHELL, OF iZEhIElIlilIil'WICH IONNECTICUT.

MANUFACTURE OF LITHOPONE 'No Drawing.

To atjv ham it may concern:

Be it known that I, JOHN L MITCHELL; a

-citizen of the United States, anda resident of Greenwich, in the county of Fairfield and 5 State of Connecticut, have invented new. and useful Improvements in the Manufacture of Lithopone, of which the following is a fullclear, and exact description.

The object of the invention is .to provide produced as a recipitation from a solution .ofjbarium sul dan d'zin'c sulfate, the pre- This'productwas subse uelntly washed, dried and calcined 1n a mu e furnace at a temperature of from 500 vto '700- C'., and

then the product was quenched in cold water,'

dried and ground'irifa.pulverizing mil'l'to form a marketable 'lithOp IieL Lithopone made in the manner' described isno't thorJ- oug' hly calcined; owing to the lumpy .condltinn of thematerial which prevents the heat from permeating the entire mass and owing to this imperfect calcinatiou loss of-density and opacity is the-r' esult. V

In my'process the precipitate formed of barium sulfate and 'zinc sulfidiis dried and Specification of Letters Patent.

I other means and. is then place mufile'furna'ce to calcine the product, then cipitate being barium sulfate and zinc su'lv fi barium sulfate and zinc sulfi izing the resultantproduct and calcining 1t ile 75' Patented O t. 19, 1920.

Application filed August 20,"1918. Serial No. 250,708.

thenthoroughly pulverized by (grinding or 40 in an airtight muffle and calcined at a temperature of from 700 to 950 C," During this cal cmatlon the pigment is constantly stirred by raking or otherwise agitating the same to allowthe heat to permeatethe whole mass thus insuring .a thorough calcination. After i the calcination ;operation-is completed the product is uenched in-cold water and made ready, for t e market in the usual manner. Lithopone produced in the manner described is .of the desired density and bpacity with a corresponding increase in the'quality. Having thus" described. my. invention, I claim as new and desire to secure by Letters Patenttv p p '1. The herein described process for manufacturing. lithopone' which consists in washing and drying aproduct formed of barium sulfate and zinc sulfid,ithen pulverizing' this product; then subjecting" it -'si-v multaneo'usly .to heat and agitation in a mufile *furnace to .caalcine the roduct, thengnenching. it in cold water a mg it. v I "2 In the preparation .oflithopone; the steps of first drying a wet precipitate oribarium sulfate and zinc sulfid, then pulverizing the resultant. product and calcining it whileagitating it. I p

3. In the preparation of lithopone,- the. steps 'of' first drying a wet. dprec pitate of then. pulverfinally dryat a temperature of700? to 950 C. w. agitating it.

0 JOHN MITCHEL 

